Monday 21 January 2013 MorningA2 GCE BIOLOGYF215/01 Control, Genomes and Environment

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OCR 2013 [F/500/8554]DC (NF/SW) 69841/4 R

Candidates answer on the Question Paper.

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Other materials required: Electronic calculator Ruler (cm/mm)

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Duration: 2 hours

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Answer all the questions.

1 Domestic chickens have been bred for many years to increase the number of eggs laid by the females. It is useful to be able to identify the young female chicks on the day after they hatch, as only the females need to be kept for laying eggs.

Unlike mammals, where the sex chromosomes are known as X and Y, in chickens the sex chromosomes are known as Z and W.

Male chickens have two Z chromosomes (ZZ).

Female chickens have one Z chromosome and one W chromosome (ZW).

(a) Some genes for feather colour and pattern in chickens are carried on the Z chromosome but not on the W chromosome. One such example is the gene for striped feathers (barring).

State the name given to this type of inheritance.

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(b) Inheritance of the barring pattern can be used to identify female chicks when they are one day old.

The phenotypes associated with the two alleles of the barring gene are shown in Table 1.1.

Allele Adult phenotype Day-old chick phenotype

dominant Bblack feathers striped

with white bars(barred)

black body with a white spot on head

recessive b black feathers(non-barred) black body and head

Table 1.1

(i) State the adult phenotypes and sex of the following individuals:

ZBZb ...................................................................................................................................

ZBW ...................................................................................................................................

ZbW ................................................................................................................................... [3]

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(ii) A cross was carried out between a barred female and a non-barred male.

Complete the genetic diagram to show the parental genotypes, their gametes and the F1 genotypes. State the phenotypes of the offspring as day-old chicks.

Parent phenotypes Barred female Non-barred male

Parent genotypes......................... .........................

Gametes......................... .........................

F1 genotypes......................... .........................

F1 day-old chick phenotypes

male ............................................................................................................................

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female ..........................................................................................................................

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[5]

(c) The autosomal gene I / i shows epistasis over all other genes affecting feather colour in chickens.

Individuals carrying the dominant allele I have white feathers.

Chickens that are not white have the genotype ii.

(i) State the precise term used to describe the genotype ii.

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(ii) Predict the colour(s) of the offspring of a cross between a male homozygous barred chicken and a white female chicken with the genotype II.

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[Total: 11]

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2 The Galapagos Islands are 600 miles away from the nearest land mass, South America. They consist of 15 main islands, 3 smaller islands, and 107 rocks and islets. This collection of islands is home to many endemic species of animals and plants. This means that these species are found nowhere else in the world.

(a) Explain, using scientific terms, why a collection of small islands remote from the mainland provides optimal conditions for speciation.

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(b) In 1978, the United Nations (UN) declared the Galapagos Islands a World Heritage Site. This led to a rise in the resident human population and the number of visitors to the Islands.

Table 2.1 shows how the number of people living on and visiting the Galapagos Islands changed between 1980 and 2005.

Year Resident population Number of visitors

1980 5500 16 000

1985 7000 19 000

1990 9500 42 000

1995 12 500 58 000

2000 17 500 68 000

2005 27 500 125 000

Table 2.1

(i) Calculate the percentage increase in the number of visitors to the Galapagos Islands between 1980 and 2005.

Show your working. Give your answer to the nearest whole number.

Answer = ...................................................... % [2]

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(ii) Outline the main ways in which increased human presence and activity have put endemic species on the Galapagos Islands, and in the sea around them, at risk of extinction.

In your answer you should link the ecological pressures imposed by human activity to examples of Galapagos Island species that have been affected.

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(c) In 2007, the United Nations (UN) put the Galapagos Islands on its Red List of endangered sites. The Galapagos governments response to this action included making new laws and placing restrictions on human activity, issuing eviction orders and culling introduced species of animals.

Suggest one economic and one ethical problem that might have arisen from this 2007 UN decision.

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[Total: 13]

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3 A student who was interested in animal behaviour did a days work experience at a zoo. He made these notes about some examples of animal behaviour that he observed.

A When I approached the otterenclosure tapping a bucket offood, the otters made rapidsqueaking noises and ran to thedoor to meet me!

B A mother duck escaped fromher enclosure and all her babyducklings followed her through ahole in the wire.

C I moved a log in one enclosureand noticed that the woodlice,which had been restingunderneath the log, began tomove around quickly once the logwas lifted.

D A banana had fallen a shortdistance away from thechimpanzee pen. A chimpanzeeused a stick to reach out and dragthe banana towards her.

E The ring-tailed lemurs showedmutual grooming behaviour,taking it in turns to searchWKURXJKDQRWKHUOHPXUVIXUIRUparasites.

F Cockroaches living in the darkin the house for nocturnal animalsran away from the light of mytorch.

G Zoo deer are free to roamamongst the visitors. Althoughdeer usually run away fromhumans, the zoo deer do not.

H When a chimpanzee threw anapple at the keeper, the keeperducked his head very fast.

Match the examples AH to the names of different types of behaviour by writing the correct letter beside the name. One has been done for you.

1 social behaviour.........

2 kinesis.........

3 imprinting.........

4 escape reflex H.........

5 taxis.........

6 operant conditioning.........

7 habituation.........

8 insight learning.........

[7]

[Total: 7]

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4 Rhubarb, Rheum x hybridum, is a plant that is grown for its edible stems. In Spring, the stems and leaves grow from fleshy roots which survive the Winter underground.

Growers have developed many new varieties of rhubarb by growing plants from seed, choosing the best young plants and then asexually reproducing them.

Seeds are produced by sexual reproduction and the rhubarb plants that grow from seed show variation in characteristics such as stem colour, dormancy period and the concentration of oxalic acid in their leaves.

(a) Outline the events that lead to genetic variation in gametes and in the plants grown from seed.

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(b) Traditionally, rhubarb plants have been produced by vegetative propagation. The best young rhubarb plants are allowed to grow for three seasons until their underground root systems are large enough. They are then dug up in Winter, the roots are cut into pieces and the pieces are replanted. Each piece is then able to grow into a new rhubarb plant that is identical to the parent.

(i) State the biotechnological term for this type of vegetative propagation.

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(ii) A gardener wished to multiply his rhubarb plants using the traditional method, but he discovered that his plants were infected by a virus.

Name the modern technique which allows commercial growers to produce large numbers of genetically identical plants that are also virus-free.

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(iii) Rhubarb plants must spend seven to nine weeks at a temperature below 3 C in order to break their winter dormancy and allow them to start growing stems and leaves again.

The length of the cold period that is required depends on the variety of rhubarb.

In the variety Timperley Early, the length of the cold period is shorter, so the plants grow and produce a crop earlier in the year than the variety Victoria.

Suggest two ways in which the varieties may differ from one another biochemically to account for the difference in the length of the cold period required by each.

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Question 4(c) begins on page 10

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(c) Rhubarb leaves contain oxalic acid, a relatively strong acid which is soluble in water and alcohol. High concentrations of oxalic acid makes rhubarb leaves poisonous to humans and other animals.

(i) The amount of oxalic acid in the leaves varies according to the variety of rhubarb, the age of the plant and environmental factors.

Suggest and plan an experiment to compare how the variety of rhubarb affects the amount of oxalic acid in rhubarb leaves.

Include in your plan:

the variables that you could control an outline of the experimental procedure you would use any measurements that you would make.

In your answer you should make clear which are the independent, dependent and controlled variables.

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..................................................................................................................................... [6] (ii) As rhubarb leaves are poisonous, they are cut off when the stems are harvested and

may be left to decompose on the compost heap.

Outline the role of decomposers in the decomposition of leaves.

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..................................................................................................................................... [3] (d) An early harvest of rhubarb stems can be obtained by placing an upturned bin over the root

when it comes out of dormancy, so the emerging shoots are kept in the dark. The shoots then grow more quickly to a height suitable for picking.

Use your knowledge of plant growth regulators (plant hormones) to suggest why shoots kept in the dark grow taller than those left in the light.

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5 Growth and development in organisms is controlled by a number of mechanisms that operate at the cellular level. The control elements involved in these mechanisms include hormones, the second messenger molecule cyclic AMP and regulatory genes.

In eukaryotes the most important regulatory genes contain homeobox sequences and are called homeotic genes.

The regulatory genes of the lac operon in prokaryotes are studied to help us to understand how regulatory genes and their products interact to switch structural genes on and off.

(a) Use your understanding of the biochemical identity and interactions of these control elements to complete Table 5.1 by putting a tick (9) or a cross (8) in each box.

Some of the boxes have been completed for you.

Control element Made of protein Binds with a proteinCodes for

protein

insulin 9cyclic AMP 8lac I (inhibitor) gene 9lac O (operator) gene 8homeotic gene product 8

[5]Table 5.1

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(b) RNA polymerase and DNA polymerase are both enzymes. RNA polymerase is involved in the action of some control elements, whereas DNA polymerase is not.

Describe and explain the difference between the functions of these two enzymes.

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(c) Another mechanism that can act to change the body plan of an organism during its development is programmed cell death.

Fill in the gaps in the following passage describing this process and the importance of its regulation.

Programmed cell death is known as ............................................... . Firstly, the fine network

of protein filaments and microtubules known as the ........................................... , which gives

structure to the cell, is broken down and digested by ............................................. .

The plasma (cell surface) membrane then changes, forming small bulges called blebs.

The cell breaks into membrane-bound fragments that are removed by the process of

................................................... so that harmful substances are not released into

surrounding tissues.

Programmed cell death is a controlled process. However, mutation in a gene called p53

can prevent programmed cell death. When this occurs, the rate at which somatic cells

are produced by the process of ...................................................... becomes greater than

the rate at which cells die, resulting in the formation of a mass of cells known as a

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6 Microorganisms are often used in biotechnological processes.

Fig. 6.1 shows the standard growth curve for a culture of bacteria.

P

Q

Time

Log numberof bacteria

R

S

Fig. 6.1

(a) Identify the phases labelled P, Q and R in Fig. 6.1.

P ............................................................................

Q ............................................................................

R ............................................................................ [3]

Metabolic processes taking place in bacteria grown in a batch culture produce primary and secondary metabolites.

(b) Explain what is meant by a primary metabolite.

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(c) With reference to the information in Fig. 6.1, state the phase or phases, P, Q, R or S, when

(i) primary metabolite production is at its highest rate;

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(ii) most secondary metabolites are produced;

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(iii) the concentration of secondary metabolites reach a maximum.

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(d) Some aerobic recombinant bacteria were grown in a fermenter. They synthesised the protein human growth hormone (HGH).

(i) Suggest two ways in which named factors inside the fermenter could be adjusted in order to maximise the yield of HGH.

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(ii) HGH made in this way is given by injection to some children who have a genetic mutation. The mutation means that they do not produce enough HGH to enable them to grow at the normal rate.

Explain why injecting recombinant HGH in this way is not an example of gene therapy.

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[Total: 15]

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7 (a) A number of new techniques for manipulating cells and genomes are now available, and it is hoped this manipulation will allow cures for diseases to be developed.

Five goals that scientists would like to achieve are described below and are listed A to E:

A producing large numbers of genetically identical model transgenic mice that show symptoms of diabetes

B growing a replacement kidney identically tissue-matched to an individual patient

C obtaining replacement hearts from transgenic pigs, partially tissue-matched to humans

D genetically manipulating cells of one adult to cure a genetic disease in that individual

E altering a prokaryotic pathogen for use as a vaccine.

The names of the procedures corresponding to four of the five goals A to E are written below.

Match the correct letters to the names. No letter should be used more than once.

xenotransplantation ................

somatic gene therapy ................

non-reproductive cloning ................

animal reproductive cloning ................ [4]

(b) Table 7.1 shows four different combinations of techniques used to achieve goals A to E. Write the letters A, B, C, D or E in the first column of the table to match each goal to the

appropriate combination of techniques needed to achieve it.

Use each letter only once.

Technique

Goal Vector used to transfer genesEmbryonic stem cells

manipulated

Non-embryonic stem cells

manipulated

Tissue designed for use in a

different species

9 8 9 89 9 8 88 9 8 89 9 8 99 8 8 8

[5]Table 7.1

[Total: 9]

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8 Earthworms are abundant in fertile soil where they play an important role in the transfer of energy in the ecosystem. An example of a food chain involving earthworms is shown in Fig. 8.1.

buckthorn leaf

earthworm

blackbird

hawk

Fig. 8.1

(a) Define the following terms:producer ....................................................................................................................................

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consumer ..................................................................................................................................

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trophic level ...............................................................................................................................

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(b) One way of measuring the abundance of earthworms is as follows:

place quadrat frames of known area onto the ground pour a chemical solution onto the soil to cause the earthworms to come up to the

surface wait and then count the earthworms.

Researchers used this technique in 2004 and 2006 to compare the abundance of earthworms in four areas of soil:

soil underneath buckthorn plants soil underneath honeysuckle plants bare soil after the removal of buckthorn plants bare soil after the removal of honeysuckle plants.

The results are shown in Fig. 8.2.

140

120

100

80

60

40

20

0July2004

July2006

July2004

buckthorn honeysuckle

July2006

mean earthwormabundance

(number m2)

soil underneath plantssoil with plants removed

Key

Fig. 8.2

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(i) Suggest two variables which the researchers should have controlled in order to make the results comparable.

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(ii) Evaluate, with reference to the error bars in Fig. 8.2, whether the data show a valid difference in the abundance of earthworms between the soil underneath honeysuckle and soil with honeysuckle removed sites for July 2004.

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(iii) Ecosystems can be described as dynamic.

State two pieces of evidence from Fig. 8.2 that show that the ecosystem is dynamic.

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[Total: 9]

END OF QUESTION PAPER

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